Cassia alata leaf extract induces cytotoxicity in A549 lung cancer cells via a mechanism that is caspase 8 dependent

Objective: To evaluate the cytotoxic effect of a hexane extract of Cassia alata leaves in A549 lung cancer cells. Method: Parental A549 lung cancer cells were exposed to various concentrations (100-180 μg/ml) of Cassia alata leaf extract for 24 hours. Following treatment, the cells were evaluated using the 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay to determine the cytotoxic effect of the extract. Caspase 8, 3 and 9 negative A549 cells were also prepared using lentiviral based shRNA knockdown of the caspase 8, 3 and 9 genes, respectively. The cytotoxic effect of Cassia alata leaf extract was then evaluated in these knockdown cells using the MTT assay. Chemical analysis was performed on the extract using high performance liquid chromatography (HPLC). Results: Cassia alata extract was cytotoxic in parental and caspase-9 negative, but not caspase 3 and 8 negative A549 cells. The IC ₅₀ values were 143 μg/ml and 145 μg/ml in parental and caspase 9 negative A549 cells respectively. The flavanoid kaempferol was identified as a constituent of Cassia alata leaf extract. Conclusions: Cassia alata produces cytotoxicity in A549 cancer cells that is mediated by caspase 8 activation. This effect may be attributable to kaempferol.